Oxygen reduction behavior of highly porous non-noble metal catalysts prepared by a template-assisted synthesis route

Highly porous non-noble metal catalysts have been prepared by template-assisted synthesis, a nanocasting procedure. A mesoporous silica gel was used to prepare different oxygen reduction catalysts. The synthesis procedure consists of the following steps: impregnation of the template with different transition metal salts (FeCl3 or CoCl2), pore filling of the impregnated host material with pyrrole, polymerization of pyrrole with hydrochloric acid and subsequent carbonization in argon as well as final liberation of the catalyst material by dissolving the template framework and the transition metal in hydrofluoric acid. The obtained catalyst samples are highly porous and exhibit outstanding oxygen reduction behavior. The Brunauer, Emmett, and Teller method surface areas between 670 and 1030 m(2)/g and pore volumes ranging from 1.6 to 2.4 cm(3)/g have been observed. Onset potentials up to 0.85 V were recorded during the oxygen reduction reaction (ORR). Different parameters affecting ORR activity (e.g., metal source, metal concentration of host material, annealing temperature) have been investigated and are discussed. Corresponding non-noble metal catalysts have been characterized by X-ray diffraction measurements, elemental analysis, scanning electron microscopy, and nitrogen adsorption. (C) 2008 The Electrochemical Society.